A population of red candidate massive galaxies ~600 Myr after the Big Bang

TL;DR

This study uses JWST observations to identify candidate massive galaxies within 750 million years after the Big Bang, revealing a higher-than-expected stellar mass density early in cosmic history.

Contribution

It reports the discovery of six candidate massive galaxies at redshifts 7.4 to 9.1, including one with a potential stellar mass of 10^11 solar masses, using JWST's infrared capabilities.

Findings

Six candidate massive galaxies identified at 7.4 < z < 9.1

Potential stellar mass of up to 10^11 solar masses for one galaxy

Stellar mass density in early galaxies may be higher than previously estimated.

Abstract

Galaxies with stellar masses as high as $\sim 10^{11}$ solar masses have been identified out to redshifts $z \sim 6$, approximately one billion years after the Big Bang. It has been difficult to find massive galaxies at even earlier times, as the Balmer break region, which is needed for accurate mass estimates, is redshifted to wavelengths beyond $2.5\mum$. Here we make use of the $1-5\mum$ coverage of the JWST early release observations to search for intrinsically red galaxies in the first ~750 million years of cosmic history. In the survey area, we find six candidate massive galaxies (stellar mass $>10^{10}$ solar masses) at $7.4 < z < 9.1$, 500 - 700 Myr after the Big Bang, including one galaxy with a possible stellar mass of $\sim 10^{11}$ solar masses. If verified with spectroscopy, the stellar mass density in massive galaxies would be much higher than anticipated from previous studies based on rest-frame ultraviolet-selected samples.